---
id: CVE-2026-104083
title: >-
  SmarterMail before build 9777 contains a stored mutation cross-site scripting
  vulnerability that allows remote attackers to inject executable script by
  placing payloads inside a <style> element nested within MathML foreign content
  (<math…
summary: >-
  SmarterMail before build 9777 contains a stored mutation cross-site scripting
  vulnerability that allows remote attackers to inject executable script by
  placing payloads inside a <style> element nested within MathML foreign content
  (<math…
severity: medium
cvss: 6.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
published: '2026-10-09'
updated: '2026-10-09'
sourceUpdated: '2026-10-09T17:06:17.770'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-104083'
references:
  - url: >-
      https://www.smartertools.com/smartermail/release-notes/current#/9526:~:text=Build%209777%20(Oct%208%2C%202026)
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/smartermail-build-9777-stored-mutation-xss-via-mathml-foreign-content
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-10-09T17:04:42.806Z'
---

## Overview

SmarterMail before build 9777 contains a stored mutation cross-site scripting vulnerability that allows remote attackers to inject executable script by placing payloads inside a <style> element nested within MathML foreign content (<math><mtext><mglyph>), which the custom HTML sanitizer treats as inert CDATA text but browsers reparse as live markup. Attackers can deliver a crafted calendar (iCal) message containing an <img src=x onerror=...> payload that executes automatically in the recipient's webmail session at /interface/message-iframe when the message is opened, enabling script execution and data exfiltration unconstrained by the interface's permissive Content-Security-Policy.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.